Method and apparatus for manufacturing annular workpieces of metal, particularly steel, to be subsequently shaped by cold forging



`Iuly 28, 1964 .scHAMlNG 3,142,115

- ramon AND APPARATUS uANuFAcTu c ANNULAR woRxPIEcEs oF METAL, PARTICULARLY STEEL, BE suBsEQUENTLy SHAPED BY coun FoRGING Filed Ju1y 7, 1961 /Nl/f N OP GUILLAUME SCHAMNG mwa wat 704m ATTORNEYS l bh- United States Patent O METHOD AND APPARATUS FOR MANUFACTUR- ING ANNULAR WORKPIECES OF METAL, PAR- TICULARLY STEEL, TO BE SUBSEQUENTLY SHAPED BY COLD FORGING j Guillaume Schaming, Le Perreux, Seine, France, assignor to Caltexa Trust, Vaduz, Liechtenstein Filed July 7, 1961, Ser. No. 122,555 Claims priority, application Germany July 15, 1960 8 Claims. (Cl. 29-416) This invention relates toa method and apparatus for manufacturing annular workpieces of metal, particularly of steel, which are to be subsequently shaped by cold forging in a press. The starting material is a circular disc or a rod section, from which a concentric inner portion is punched out by means of a punch in a die.

In the manufacture of annular blanks for forgings from rod sections or thick circular discs by punching as indicated above, it has been found in practice that an unclean cut is obtained because burrs, cracks or overlaps tend to form at the surface of cut during punching. These faults in the material are extremely detrimental during the subsequent shaping by cold forging and may lead to rejects. To avoid this disadvantage, it has previously been necessary to machine the unclean cut obtained by punching before performing the cold-forging operation. This machining is an additional operation, which increases the cost of cold-forged workpieces.

It is an object of the invention to improve the punching operation in order to ensure that the punching of a concentric inner part from a rod section or a thick circular disc will result in an absolutely clean cut so that the blank can be readily subjected to subsequent shaping by cold forging, without intermediate machining. According to the invention, this is achieved in that the diameter difference between the cutting edges of the punch and of the die is about one fourth of the thickness of the blank so that an inclination of about 7 and more results between the two cutting edges in the parting direction; i.e., the radial clearance being about one-eighth of the thickness of the blank. With this punch clearance, the cutting operation will result in a clean cut at the separated work-piece parts (inner part and outer ring). The two separated parts of the blank, namely, the outer ring and the solid central part, are given such a volume and dimension that they are appropriately pre-shaped for the subsequent shaping. According to the invention, a single starting blank may be repeatedly punched as indicated above to form from the resulting solid central portion further annular workpieces for the subsequent forging. This may be suitable, e.g., if the punched annular members are to be used as inner and outer races of anti-friction bearings or are to be combined in a similar unit (screwed pipe coupling or the like). The subsequent shaping of the solid central part of the starting blank will result in an optimum utilization of material.

In the accompanying drawing, an illustrative embodiment of the invention is shown.

FIG. 1 is a diagrammatical view showing the punching tool with the inserted blank before the beginning of the punching.

FIG. 2 is a sectional view showing a pre-shaped blank (pressing).

FIG. 3 shows the same blank after punching, whereby it has been separated into an outer ring and a solid central part.

FIG. 4 is a longitudinal sectional view showing the entire punching tool.

FIG. 5 shows a screwed pipe joint consisting of coldforged annular members.

FIG. 6 shows an anti-friction bearing consisting of cold-forged annular members.

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FIG. 7 shows a pipe coupling,pthe annular parts of which have bearing shoudlers.

The starting blank for use in the method according to the invention 'is a circular disc 1 which is obtained by flatpressing a rod section to exact shape and has the height h. This discis insertedinto an open die 2, the annular shoulder 2 of which serves as a support for the disc. The edge 2"' of theannular shoulder formsl a cutting edge. The punch 3 engages the top endface of the disc 1. The punch has such a diameter d that a cutting clearance s amountingto approximately one-eighthof theheight h of the blank is obtained relative to the die diameter D. With this cutting clearance s, the desc'ent of the punch 3 will result in a cut 4 having an inclination of ab out7 between the parts of the blank 1 to be separated. These conditions ensure that the separation of the parts of the blank (outer annular member 1a and central portion 1b)-see FIG. 3will result in a satisfactory cut without burr or overlaps so that the separated blank parts can be subsequently shaped to the desired workpiece without intermediate machining. For an economical production it is desirable to separate the blank into two parts having such a volume and size that the blank parts can be readily shaped subsequently to the desired final shape (workpiece). For this purpose, it is recommendable to exactly pre-shape the blank 1, e.g., by trueing it to exact volume and size, e.g., by forming depressions 5, 6 in its end faces, as is shown in FIG. 2.

As has already been indicated, another annular member and central part of smaller size may be made from the punched solid central part 1b (FIG. 3) in a subsequent punching operation. This separating operation may be repeated as often as the cutting conditions permit. This method of manufacture is of advantage if the annular members obtained by punching and having different diameters are combined in a unit of construction (anti-friction bearing, pipe connection and the like). See FIGS. 5, 6 and 7.

FIG. 4 shows the punching tool after the blank has been separated into the two parts 1a and 1b, both of which are jointly ejected from the die 2 by the ram 5. In this case, it is also of advantage that the inclination of the cut between the two parts 1a, 1b is larger than the angle of friction. As a result, the outer ring 1a is carried along by the central part as the ram 5 rises whereas the separated parts of the blank are not wedged one into the other.

What I claim is:

l. A method of manufacturing annular workpieces of metal from a solid blank, which comprises punching a concentric inner part from said blank by means of a punch and die having a diameter difference which is approximately one fourth of the thickness of said blank so that a cut having an linclination of about 7 is obtained between the cutting edges of the punch and die.

2. A method as claimed in claim 1, in which said blank consists of steel.

3. A method as claimed in claim l, which comprises pre-shaping said blank before punching.

4. A method as claimed in claim 1, in which the annular member remaining after punching is subsequently coldforged.

5. A method of manufacturing assemblies of annular workpieces of metal disposed one in the other, which comprises punching a concentric inner part from a solid blank by means of a punch and die having a radius dimension cutting edge clearance which is approximately one-eighth of the thickness of said blank so that a cut having an inclination of about 7 is obtained between the cutting edges of the `punch and die, to divide said blank into a solid inner member and an annular member, repeating said operation on said solid inner member serving as a blank, cold-forging the annular members thus obtained, and assembling said annular members one in the other.

6. A punching tool for manufacturing annular Workthickness, which comprises a punch and die adapted to cooperate in punching a cencentric inner part from said blank, said punch and die having a diameter dimension dilerence which is approximately one fourth of said predetermined thickness. 7. A punching tool as claimed in claim 6, which comprises a ram disposed opposite to said punch with respect to said die and operable to jointly eject the separated parts of the blank out of the die in the direction toward said punch.

8. A punch and die assembly for making annular workpieces from a blank; said punch and die assembly being characterized in that `the following relationships obtain:

where References Cited in the le of this patent UNTED STATES PATENTS 37,189 Westlake Dec. 16, 1862 1,387,638 Bingham Aug. 16, 1921 1,971,083 Schlaa Aug. 2l, 1934 2,383,584 Beishline et al Aug. 28, 1945 

5. A METHOD OF MANUFACTURING ASSEMBLIES OF ANNULAR WORKPIECE OF METAL DISPOSED ONE IN THE OTHER, WHICH COMPRISES PUNCHING A CONCENTRIC INNER PART FROM A SOLID BLANK BY MEANS OF A PUNCH AND DIE HAVING A RADIUS DIMENSION CUTTING EDGE CLEARANCE WHICH IS APPROXIMATELY ONE-EIGHT OF THE THICKNESS OF SAID BLANK SO THAT A CUT HAVING AN INCLINATION OF ABOUT 7* IS OBTAINED BETWEEN THE CUTTING EDGES OF THE PUNCH AND DIE TO DIVIDE SAID BLANK INTO A SOLID INNER MEMBER AND AN ANNULAR MEMBER, REPEATING SAID OPERATION ON SAID SOLID INNER MEMBER SERVING AS A BLANK, COLD-FORGING THE ANNULAR MEMBERS THUS OBTAINED, AND ASSEMBLING SAID ANNULAR MEMBERS ONE IN THE OTHER. 